My objectives in seeking a KGB career development award are two-fold: 1) to examine the multipotentiality of post-natal human keratocytes and human neural crest stem cells in ovo and; 2) to develop my career as an independent investigator in stem cell biology by hands-on research experience, didactics and mentorship. The most common causes of human corneal blindness are visually significant stromal scarring and endothelial cell dysfunction. In the US, it is predicted that with the advent of refractive surgery, the supply of donor corneas suitable for transplantation will be significantly reduced. Because of these challenges, there is significant interest in pursuing the use of cells that have the ability to self-renew, differentiate into multiple cell lineages, and remodel tissues in vivo, in the treatment of corneal disorders. While there have been recent reports of human cornea stem cells that can be induced to express markers consistent with multi- potency in cell culture, little is known about the multi-potentiality of differentiated cornea stromal cells. Our preliminary data indicate that human keratocytes isolated from postnatal corneas have the ability to differentiate into neural crest derivatives in the chick embryonic environment. This is the first evidence, albeit early, that human keratocytes and postnatal (versus embryonic) keratocytes retain the multi-potentiality of the neural crest precursors from which they are derived as partially restricted progenitors. The working hypothesis of this proposal is that human postnatal keratocytes retain the multi-potency of their neural crest precursors and have the ability to differentiate into neural crest derivatives, including other ocular tissues. Further, the chick embryonic microenvironment likely contains the adequate signals required to differentiate human neural crest stem cells into ocular tissues, as well as other neural crest-derived structures. Three specific aims will be addressed; Aim 1; characterize the multipotentiality of human post-natal keratocytes, using the chick embryonic environment as an assay system. Aim 2: examine the effects of age and differentiation status on the multipotentiality of human keratocytes. Aim 3; explore the potential for human neural crest stem cells to form neural crest ocular derivatives in ovo. RELEVANCE (See instructions); The availability of donor corneas often limits the ability to treat corneal scarring, the second most common cause of blindness worldwide. Our goal is to understand the ability of post-natal human keratocytes and neural crest stem cells to differentiate into ocular tissues in an embryonic environment. This will serve as a basis for determining the feasibility of creating specialized cells for use in regenerative medicine.